Transconnector for coupling spinal rods

ABSTRACT

The present invention is directed to a transconnector for coupling first and second spinal fixation rods or other elongate fixation elements. The transconnector includes a male member, a female member, and a locking member. The male member has a body with a linking element (such as a hook) associated with the lateral end for receiving one of the fixation elements, and a projection extending from the medial end. The female member has a body with a linking element associated with the lateral end for receiving the other fixation element, and a cavity with an opening on the medial end for receiving a portion of the male member projection. The locking member adjustably and rotatably secures the male member projection portion in the cavity in order to accommodate different orientations and separation distances between the first and second fixation elements. The male member may be made as a two component assembly in which the two components can rotate relative to one another for accommodating rod convergence or divergence.

FIELD OF THE INVENTION

The present invention relates to a device for spinal fixation, and inparticular to a transconnector for coupling spinal rods, plates, orother elongate members.

BACKGROUND OF THE INVENTION

It is often necessary to surgically treat spinal disorders such asscoliosis. Numerous systems for use in spinal correction and fixationhave been disclosed. These systems usually include a pair of elongatemembers, typically either rods or plates, placed on opposite sides ofthe vertebral column. Each rod is attached to the spine with variousattachment devices. These attachment devices include pedicle screws,plates, spinous process hooks, sublaminar hooks, and pedicle hooks.

It is also well known that the strength and stability of the dual rodassembly can be increased by coupling the two rods with a cross-brace ortransconnector which extends substantially horizontal to thelongitudinal axes of the rods across the spine. The simplest situationin which a transconnector could be used occurs when the two rods aregeometrically aligned. Specifically, the two rods are parallel to eachother, i.e. there is no rod convergence or divergence in themedial-lateral direction; the two rods have the same orientation withrespect to the coronal plane in the anterior-posterior direction, i.e.the rods are coplanar from a lateral view; and the two rods are locateda fixed, predetermined distance from each other.

Due to a wide variety of factors, the two rods are rarely geometricallyaligned in clinical situations. There are several ways to address thevariations from geometrical alignment. First, one or both of the rodscan be bent to accommodate the transconnector. However, any bending ineither of the rods can adversely affect the fixation to the spine andcomprise clinical outcome. Furthermore, the bending can also adverselyaffect the mechanical properties of the rods. The transconnector canalso be bent so that the disturbance to the rod positioning isminimized. As was the case with bending of the rods, the mechanicalproperties of the transconnector could be compromised.

Transconnectors with some adjustability have been designed to adapt forvariations from geometrical alignment. However, most are multi-piecesystems that can be difficult to assemble and use in the surgicalenvironment. Even those that are one-piece designs do not allow foradjustments to compensate for all three modes in which there may bevariation from geometrical alignment: convergence or divergence,non-coplanar rods, and variability in rod separation distances.

Thus, there exists a need for an improved transconnector for couplingspinal rods.

SUMMARY OF THE INVENTION

The present invention relates to a transconnector for coupling first andsecond elongate spinal fixation elements that have differentorientations with respect to a plane. The transconnector includes a malemember, a female member and a locking member and can be made of anysuitable material such as titanium, a titanium alloy, or stainlesssteel. The male member comprises a body with lateral and medial ends, alinking element associated with the lateral end and being configured anddimensioned to receive one of the fixation elements, and a projectionextending from the medial end. The female member comprises a body withlateral and medial ends, a linking element associated with the lateralend and being configured and dimensioned to receive one of the fixationelements, and a cavity with an opening on the medial end which isconfigured and dimensioned to receive a portion of the male memberprojection. The locking member adjustably and rotatably secures the malemember projection portion in the cavity in order to accommodatedifferent orientations and separation distances between the first andsecond fixation elements.

In a preferred embodiment, the male member projection is substantiallycylindrical and has a pin extending perpendicularly from itslongitudinal axis. The pin is slidable in a slot located in a wall ofthe female member cavity for adjusting the portion of the projectionreceived in the cavity. The slot has a width which is wider than thediameter of the pin so that the projection can rotate in the cavity. Inorder to further increase the degree of rotation, the side edges of theslot may angle outwardly.

Preferably, the locking member comprises a threaded hole in the body ofthe female member and a set screw threadably received in the threadedhole. The set screw has a first end for receiving a tool to turn the setscrew and a second end contactable with the projection for pressing theprojection against the cavity.

The male member body may comprise a link terminal having a lateral endwith the male member linking element, an intermediate link having amedial end with the projection of the male member and a lateral endengaging the medial end of the link terminal, and a locking element forsecuring the link terminal to the intermediate link. Preferably, themedial end of the link terminal includes a first textured surface andthe lateral end of the intermediate link includes a second texturedsurface mating with the first textured surface. The first texturedsurface is rotatable with respect to the second textured surface foraccommodating convergence or divergence between the first and secondrods. An example of suitable first and second textured surfaces includesa star-grind pattern.

The locking element preferably comprises a first hole through the medialend of the link terminal, a second hole through the lateral end of theintermediate link aligned with the first hole, and a cap screwinsertable in the first and second holes. The cap screw may have asecond end with a retaining ring for preventing removal of the cap screwfrom the first and second holes. The retaining ring may include aresilient member which flexes inward upon insertion of the cap screwthrough the first and second holes and flexes outward once the resilientmember is past a collar in the second hole. Preferably, the resilientmember includes an end of the cap screw with a lip and a plurality ofslits.

If rods are used for the elongate fixation elements, then the malemember linking element preferably comprises a hook and the female memberlinking element preferably comprises a hook. The lateral ends of themale and female members each may include a threaded hole and a clampingscrew threadably received in the respective threaded hole for securingthe fixation elements to the respective hook. The fixation elements arepreferably clamped between a conical second body portion of therespective clamping screw and a region near the tip portion of therespective hook when the fixation elements are secured to thetransconnector.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred features of the present invention are disclosed in theaccompanying drawings, wherein similar reference characters denotesimilar elements throughout the several views; and wherein:

FIG. 1 shows a top perspective view of a transconnector according to thepresent invention with an elongate fixation element attached at eachend;

FIG. 2 shows a bottom perspective view of the transconnector without thefixation elements;

FIG. 3 shows a cross-sectional view of the transconnector with onefixation element attached;

FIG. 4 shows a perspective view of the female member of thetransconnector;

FIG. 5 shows a side view of the female member;

FIG. 6 shows a cross-sectional view of the female member taken alongline A—A of FIG. 5;

FIG. 7 shows a side view of a link terminal of the male member withportions cut out;

FIG. 8 shows a cross-sectional view of an intermediate link of the malemember; and

FIG. 9 shows a perspective view of a cap screw used to join the linkterminal and intermediate link.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a transconnector 10 according to the present invention forcoupling a first elongate spinal fixation element 12 to a secondelongate spinal fixation element 14. Transconnector 10 can be made ofany suitable material typically used in orthopaedic applications such astitanium, titanium alloy, or stainless steel. If transconnector 10 ismade of a metallic material, preferably it is the same metallic materialused for fixation elements 12, 14 to avoid galvanic (mixed-metal)corrosion. First and second fixation elements 12, 14 can be cylindricalrods, rectangular bars, plates, or any other device suitable for spinalfusion. In use, first fixation element 12 extends along one side of thevertebral column and second fixation element 14 extends along the otherside of the vertebral column. A wide variety of attachment devices suchas hooks, screws, and clamps, can be used to attach first and secondfixation elements 12, 14 to the spine.

Transconnector 10 includes a male member 16, a female member 18, and alocking member 20. Male member 16 has a body with a linking element 22on a lateral end for receiving first fixation element 12 and aprojection 24 extending from a medial end of the body. Female member 18has a body with a linking element 26 on a lateral end for receivingsecond fixation element 14 and a cavity 28 with an opening 30 (FIG. 5)on a medial end of the body for receiving a portion of projection 24.Locking member 20 secures the portion of projection 24 in cavity 28. Theportion of projection 24 received in cavity 28 is adjustable foraccommodating different separation distances d between first and secondfixation elements 12, 14. This feature allows transconnector 10 to bereadily adjusted for different patient anatomies and used in differentregions of the spine. For example, the lumbar vertebrae are typicallylarger than the thoracic vertebrae. As a result, the distance betweenfixation elements in the lumbar region would be greater than fixationelements in the thoracic region. Because the length of projection thatslides into cavity 28 can be changed, transconnector can be adjusted foruse in different spinal regions without the need to bend either fixationrods or transconnector 10. In order to further increase theadjustability of transconnector 10, female member 18, cavity 28, andprojection 24 can be manufactured in different sizes.

Projection 24 is rotatable in cavity 28 for accommodating differencesbetween the angular orientation of first fixation element 12 withrespect to the coronal plane and the angular orientation of secondfixation element 14 with respect to the coronal plane. Specifically,first fixation element 12 has a longitudinal axis L₁ which runs at anangle α₁, with respect to coronal plane C and second fixation element 14has a longitudinal axis L₂ which runs at an angle α₂ with respect tocoronal plane C, the plane which divides the body in half from front toback. Because projection 24 can rotate in cavity 28, transconnector canbe used in situations in which α₁, differs from α₂ without the need tobend either fixation element or transconnector 10.

As seen best in FIGS. 2, 3, and 5, projection 24 is substantiallycylindrical and cavity 28 has a corresponding shape to facilitaterotation of projection 24 in cavity 28. Projection 24 has a pin 32extending perpendicularly therefrom which travels within a slot 34located on a wall 36 of cavity 28. The engagement of pin 32 with frontand back edges 38 limits the length of projection 24 that can slide incavity 28 and prevents projection 24 from coming completely out ofcavity 28. Because the diameter of pin 32 is smaller than the width ofslot 34, projection 24 can rotate in cavity 28. The engagement of pin 32with side edges 40 limits the amount of rotation of projection 24 incavity 28. Side edges 40 can angle outward to increase the angle ofrotation β as shown in FIG. 6. A β of 45° should be sufficient toaccommodate even the most extreme differences between α₁, and α₂.

As previously noted, locking member 20 secures the portion of projection24 in cavity 28. FIGS. 1, 3, and 5 show that locking member 20 includesa threaded hole 42 in female member 18 and a set screw 44. Set screw 44threads into threaded hole and a second end 46 of set screw 44 pressesprojection 24 to clamp it against the walls of cavity 28. A first end 48of set screw 44 has an appropriately shaped and sized hole 50 (or aslot) for receiving a surgical instrument like a screwdriver to turn setscrew 44.

FIGS. 1, 7, and 8 show the body of male member 16 as a two pieceassembly which includes a link terminal 52, an intermediate link 54, anda locking element 56 to secure the two together. A lateral end of linkterminal 52 has male member linking element 22 and intermediate link 54has a medial end with projection 24 and a lateral end 58 which engages amedial end 60 of link terminal 52. Medial end 60 of link terminal 52includes a first textured surface 62 which mates with a second texturedsurface 64 of lateral end 58 of intermediate link 54 in such a fashionthat first textured surface 62 is rotatable with respect to secondtextured surface 64 to accommodate for any convergence or divergencebetween first and second fixation elements 12, 14. First and secondtextured surfaces 62, 64 are provided with a plurality of teeth, such asa star-grind pattern, in order to help maintain link terminal 52 at thedesired angular orientation. Locking element 56 includes a first hole 66through medial end 60 of link terminal 52 and a second hole 68 throughlateral end 58. First and second holes 66, 68 align so that a cap screw70 can be inserted therethrough.

Referring to FIG. 9, cap screw 70 has a first end 72 with a slot 74 forreceiving a tool to turn cap screw 70 and a second end 76 with aretaining ring 78 for preventing removal of cap screw 70 from first andsecond holes 66, 68. Retaining ring 78 has slits 80 which allowretaining ring to flex inward to be inserted through a collar 82 insecond hole 68. Once retaining ring 78 is inserted past collar 82,retaining ring 78 flexes back outward so that cap screw 70 can not becompletely screwed out of first and second holes 66, 68. A body 84 ofcap screw 70 is provided with threads 86 which engage threads 88 on thewalls of second hole 68.

The structure of linking elements 22, 26 will depend on the structure offixation elements 12, 14. For example, if fixation rods 12, 14 areelongate plates, then linking elements 22, 26 are configured anddimensioned to receive elongate plates. Such configurations andconfigurations for other types of fixation elements are well known inthe art. If fixation elements 12, 14 are cylindrical rods as shown inthe drawings, then linking elements 22, 26 each comprises a hook 90. Thelateral ends of male and female members 16, 18 each includes a threadedhole 92 and a clamping screw 94 threadably received in threaded hole 92for securing first and second fixation elements 12, 14 to hook 90.

As seen best in FIGS. 2 and 3, each clamping screw 94 has a first end 96with a slot 98 for receiving a tool to turn clamping screw 94, athreaded cylindrical first body portion 100, and a conical second bodyportion 102. Each hook 90 comprises a tip portion 104 and a curvedportion 106. Curved portion 106 has a radius of curvature larger thanthe radius of fixation elements 12, 14. As a result, the only contactbetween hooks 90 and fixation elements 12, 14 is at a region near tipportion 104. Furthermore, the only contact between clamping screws 94and fixation elements 12, 14 is on conical second body portion 102.Thus, fixation elements 12, 14 is clamped between conical second bodyportion 102 and the region near tip portion 104.

While various descriptions of the present invention are described above,it should be understood that the various features can be used singly orin any combination thereof. Therefore, this invention is not to belimited to only the specifically preferred embodiments depicted herein.

Further, it should be understood that variations and modificationswithin the spirit and scope of the invention may occur to those skilledin the art to which the invention pertains. Accordingly, all expedientmodifications readily attainable by one versed in the art from thedisclosure set forth herein that are within the scope and spirit of thepresent invention are to be included as further embodiments of thepresent invention. The scope of the present invention is accordinglydefined as set forth in the appended claims.

What is claimed is:
 1. A transconnector for coupling first and secondelongate spinal fixation elements that have different orientations, thetransconnector comprising: a male member comprising a link terminal thatincludes a linking element associated with a lateral end of the linkterminal and being configured and dimensioned to receive one of thefixation elements, and a first textured surface on a medial end of thelink terminal; an intermediate link comprising a projection extendingfrom a medial end of the intermediate link and a second textured surfaceon a lateral end of the intermediate link for mating with the firsttextured surface such that the first textured surface is rotatable withrespect to the second textured surface for accommodating convergence ordivergence between the first and second fixation elements, and a lockingelement for securing the link terminal to the intermediate link; afemale member comprising a body with lateral and medial ends, a linkingelement associated with the lateral end and being configured anddimensioned to receive one of the fixation elements, and a cavity withan opening on the medial end which is configured and dimensioned toreceive a portion of the projection; a locking member for adjustably androtatably securing the projection in the cavity in order to accommodatedifferent orientations and separation distances between the first andsecond fixation elements; a pin having a diameter and extendingperpendicularly from a longitudinal axis of the projection; and a slotlocated on a wall of the female member cavity, wherein side edges of theslot are configured and dimensioned to angle outwardly and the pin isslideable in the slot for adjusting the portion of the projectionreceived in the cavity and the slot has a width which is wider than thediameter of the pin to allow rotational movement of the pin in the slotand rotation of the projection in the cavity.
 2. A transconnector forcoupling first and second elongate spinal fixation elements that havedifferent orientations, the transconnector comprising: a male membercomprising a link terminal that includes a linking element associatedwith a lateral end of the link terminal and being configured anddimensioned to receive one of the fixation elements, and a firsttextured surface on a medial end of the link terminal; an intermediatelink comprising a substantially cylindrical projection extending from amedial end of the intermediate link and a second textured surface on alateral end of the intermediate link for mating with the first texturedsurface such that the first textured surface is rotatable with respectto the second textured surface for accommodating convergence ordivergence between the first and second fixation elements and a lockingelement for securing the link terminal to the intermediate link; afemale member comprising a body with lateral and medial ends, a linkingelement associated with the lateral end and being configured anddimensioned to receive one of the fixation elements, and a cavity withan opening on the medial end which is configured and dimensioned toreceive a portion of the projection; a locking member for adjustably androtatably securing the projection in the cavity in order to accommodatedifferent orientations and separation distances between the first andsecond fixation elements; a pin having a diameter and extendingperpendicularly from a longitudinal axis of the projection; and a slotlocated on a wall of the female member cavity, wherein side edges of theslot are configured and dimensioned to angle outwardly and the pin isslideable in the slot for adjusting the portion of the projectionreceived in the cavity and the slot has a width which is wider than thediameter of the pin to allow rotational movement of the pin in the slotand rotation of the projection in the cavity.
 3. The transconnector ofclaim 1 wherein the locking member comprises: a threaded hole in thebody of the female member; and a set screw threadably received in thethreaded hole and having a first end for receiving a tool to turn theset screw and a second end contactable with the projection for pressingthe projection against the cavity.
 4. The transconnector of claim 1wherein the first and second textured surfaces include a star-grindpattern.
 5. The transconnector of claim 1 wherein the locking elementcomprises: a first hole through the medial end of the link terminal; asecond hole through the lateral end of the intermediate link alignedwith the first hole; and a cap screw insertable in the first and secondholes.
 6. The transconnector of claim 5 wherein the cap screw has afirst end for receiving a tool to turn the cap screw and a second endwith a retaining ring engaging at least a portion of a collar of thesecond hole to prevent removal of the cap screw from the first andsecond holes.
 7. The transconnector of claim 6 wherein the cap screw hasa body with threads and the second hole is threaded for threadablyreceiving the cap screw.
 8. A transconnector for coupling first andsecond elongate spinal fixation elements having different orientations,the transconnector comprising: a male member comprising a link terminalthat includes a linking element associated with a lateral end of thelink terminal and being configured and dimensioned to receive one of thefixation elements, and a first textured surface on a medial end of thelink terminal; an intermediate link comprising a projection extendingfrom a medial end of the intermediate link and a second textured surfaceon a lateral end of the intermediate link for mating with the firsttextured surface such that the first textured surface is rotatable withrespect to the second textured surface for accommodating convergence ordivergence between the first and second fixation elements and a lockingelement for securing the link terminal to the intermediate link; afemale member comprising a body with lateral and medial ends, a linkingelement associated with the lateral end and being configured anddimensioned to receive one of the fixation elements, and a cavity withan opening on the medial end which is configured and dimensioned toreceive a portion of the projection; and a locking member for adjustablyand rotatably securing the projection in the cavity in order toaccommodate different orientations and separation distances between thefirst and second fixation elements, wherein: the locking elementcomprises a first hole through the medial end of the link terminal, asecond hole through the lateral end of the intermediate link alignedwith the first hole, and a cap screw insertable in the first and secondholes and having a first end for receiving a tool to turn the cap screwand a second end with a retaining ring for preventing removal of the capscrew from the first and second holes; and the second hole includes acollar and the retaining ring includes a resilient member, the resilientmember flexing inward upon insertion of the cap screw through the firstand second holes and flexing outward once the resilient member is pastthe collar for preventing removal of the cap screw.
 9. Thetransconnector of claim 8 wherein the resilient member includes an endof the cap screw with a lip and a plurality of slits.
 10. Thetransconnector of claim 1 wherein the male member linking elementcomprises a hook and the female member linking element comprises a hook.11. The transconnector of claim 10 wherein the lateral end of the malemember and the lateral end of the female member each includes a threadedhole and a clamping screw threadably received in the respective threadedhole for securing fixation elements to the respective hooks of the maleand female members.
 12. The transconnector of claim 11 wherein eachclamping screw has a first end for receiving a tool to turn the clampingscrew, a threaded cylindrical first body portion, and a conical secondbody portion.
 13. The transconnector of claim 12 wherein the hook of themale member and the hook of the female member each comprises a tipportion and a curved portion having a radius of curvature larger thanthat of fixation elements.
 14. The transconnector of claim 13 incombination with the first and second fixation elements wherein eachfixation element is clamped between the conical second body portion ofrespective each clamping screw and a region near the tip portion of therespective hook.
 15. The transconnector of claim 1 wherein thetransconnector is made of titanium, a titanium alloy, or stainlesssteel.
 16. The transconnector of claim 8 wherein the projection issubstantially cylindrical and the first and second textured surfacesinclude a star-grind pattern.
 17. The transconnector of claim 8 whereinthe male member linking element comprises a hook and the female linkingelement comprises a hook.
 18. The transconnector of claim 8 wherein thetransconnector is made of titanium, a titanium alloy or stainless.